.......Mainwindow.xaml......

<Window
    x:Class="App4.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:App4"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <StackPanel Orientation="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Center">
        <Button x:Name="myButton" Style="{StaticResource Style_Button_Common_Navigation_Overlay}" 
                     Tag="Press" Click="myButton_Click">
        </Button>
    </StackPanel>
</Window>



.......Mainwindow.xam.cs......

using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;
using Microsoft.UI.Xaml.Controls.Primitives;
using Microsoft.UI.Xaml.Data;
using Microsoft.UI.Xaml.Input;
using Microsoft.UI.Xaml.Media;
using Microsoft.UI.Xaml.Navigation;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.Foundation.Collections;

// To learn more about WinUI, the WinUI project structure,
// and more about our project templates, see: http://aka.ms/winui-project-info.

namespace App4
{
    /// <summary>
    /// An empty window that can be used on its own or navigated to within a Frame.
    /// </summary>
    public sealed partial class MainWindow : Window
    {
        public MainWindow()
        {
            this.InitializeComponent();
        }

        private void myButton_Click(object sender, RoutedEventArgs e)
        {
            myButton.Content = "Clicked";
        }
    }
}



.......ResourceDictionary1.xaml......

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:App4">

    <x:String x:Key="Icon_Path_Data_OverlayButton">M18,9.2c-0.2,0-0.4,0.2-0.5,0.5v5H6.4V3.4h5
    c0.2,0,0.4-0.2,0.4-0.5c0-0.2-0.2-0.4-0.4-0.5H6C5.7,2.5,5.5,2.7,5.5,3V15c0,0.2,0.2,0.4,0.5,0.5H18c0.2,0,0.4-0.2,0.5-0.5V9.6
    C18.5,9.4,18.3,9.2,18,9.2z M18.5,2.8c0-0.1-0.1-0.2-0.2-0.2c0,0-0.1,0-0.2,0H15c-0.2,0-0.4,0.2-0.5,0.5c0,0.2,0.2,0.4,0.5,0.5h2
    l-5,5c-0.2,0.2-0.2,0.4,0,0.6c0,0,0,0,0,0c0.2,0.2,0.5,0.2,0.7,0l5-5v2c0,0.3,0.2,0.5,0.5,0.5c0.3,0,0.5-0.2,0.5-0.5V3
    C18.5,2.9,18.5,2.8,18.5,2.8z
    </x:String>
    
    <Style x:Key="Style_Button_Common_Navigation_Overlay" TargetType="Button">
        <Setter Property="Background" Value="Transparent" />
        <Setter Property="BorderBrush" Value="Gray"/>
        <Setter Property="Foreground" Value="Green" />
        <Setter Property="BorderThickness" Value="1" />
        <Setter Property="HorizontalAlignment" Value="Left" />
        <Setter Property="VerticalAlignment" Value="Top" />
        <Setter Property="FontSize" Value="8" />
        <Setter Property="FontWeight" Value="Normal" />
        <Setter Property="Margin" Value="20,21,21,0" />
        <Setter Property="Visibility" Value="Visible" />
        <Setter Property="Opacity" Value="1" />
        
        <Setter Property="UseSystemFocusVisuals" Value="True" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="Button">
                    <Grid x:Name="RootGrid">
                        <ToolTipService.ToolTip>
                            <ToolTip Content="{TemplateBinding Tag}" FontFamily="arial" FontSize="8" Placement="Right" HorizontalOffset="7" Foreground="White" Background="Gray" CornerRadius="10"></ToolTip>
                        </ToolTipService.ToolTip>
                        <VisualStateManager.VisualStateGroups>
                            <VisualStateGroup x:Name="CommonStates">

                                <VisualState x:Name="Normal">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="SharedBorder" Storyboard.TargetProperty="BorderBrush">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="Gray" />
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="SharedBorder" Storyboard.TargetProperty="BorderThickness">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="1" />
                                        </ObjectAnimationUsingKeyFrames>
                                        <PointerUpThemeAnimation Storyboard.TargetName="RootGrid" />
                                    </Storyboard>
                                </VisualState>
                                <VisualState x:Name="PointerOver">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="SharedBorder" Storyboard.TargetProperty="BorderBrush">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="Red" />
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="SharedBorder" Storyboard.TargetProperty="BorderThickness">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="5" />
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                                <VisualState x:Name="Pressed"/>
                                <VisualState x:Name="Disabled"/>
                            </VisualStateGroup>
                        </VisualStateManager.VisualStateGroups>
                        <Border x:Name="SharedBorder"
                                    BorderBrush="{TemplateBinding BorderBrush}"
                                    BorderThickness="{TemplateBinding BorderThickness}"/>
                        <StackPanel Orientation="Horizontal" 
                                    Padding="5,5,10,5"
                                    HorizontalAlignment="Center"
                                    VerticalAlignment="Center">
                            <Path Data="{StaticResource Icon_Path_Data_OverlayButton}" Width="18" Height="18" Fill="White"/>
                        </StackPanel>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>



.......App.xaml......

<Application
    x:Class="App4.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:App4">
    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <XamlControlsResources xmlns="using:Microsoft.UI.Xaml.Controls" />
                <ResourceDictionary Source="ms-appx:///ResourceDictionary1.xaml"/>
                <!-- Other merged dictionaries here -->
            </ResourceDictionary.MergedDictionaries>
            <!-- Other app resources here -->
        </ResourceDictionary>
    </Application.Resources>
</Application>



.......App.xaml.cs......

using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;
using Microsoft.UI.Xaml.Controls.Primitives;
using Microsoft.UI.Xaml.Data;
using Microsoft.UI.Xaml.Input;
using Microsoft.UI.Xaml.Media;
using Microsoft.UI.Xaml.Navigation;
using Microsoft.UI.Xaml.Shapes;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.ApplicationModel;
using Windows.ApplicationModel.Activation;
using Windows.Foundation;
using Windows.Foundation.Collections;

// To learn more about WinUI, the WinUI project structure,
// and more about our project templates, see: http://aka.ms/winui-project-info.

namespace App4
{
    /// <summary>
    /// Provides application-specific behavior to supplement the default Application class.
    /// </summary>
    public partial class App : Application
    {
        /// <summary>
        /// Initializes the singleton application object.  This is the first line of authored code
        /// executed, and as such is the logical equivalent of main() or WinMain().
        /// </summary>
        public App()
        {
            this.InitializeComponent();
        }

        /// <summary>
        /// Invoked when the application is launched normally by the end user.  Other entry points
        /// will be used such as when the application is launched to open a specific file.
        /// </summary>
        /// <param name="args">Details about the launch request and process.</param>
        protected override void OnLaunched(Microsoft.UI.Xaml.LaunchActivatedEventArgs args)
        {
            m_window = new MainWindow();
            m_window.Activate();
        }

        private Window m_window;
    }
}